1. Field of the Invention
The present invention relates to an image processing apparatus for receiving a program and producing a composite video with an OSD image such as a menu screen superposed on a video of the received program.
2. Description of the Related Art
Conventionally, a set top box (STB) for viewing a digital broadcast program by connecting to an analog television receiver and a television receiver comprising this STB have been put to practical use. The typical STB is provided with an OSD function (on-screen display function) of displaying an OSD image such as a setting screen for various parameters superposed on the video of the program being received at present, so that the user may adjust the operation of the STB according to the users own preference. The OSD function allows the user to easily set various parameters in accordance with a guide on the setting screen displayed on a screen of the television receiver. Also, another OSD image displays not only the setting screen for various parameters but also the current time or currently selected channel at a right upper or left upper corner of the screen.
In displaying the OSD image, when two images are displayed in superposition, the video may be distorted near a boundary portion between these images, if the images to be displayed have significantly different color attribute (the attribute such as brightness, transparency and saturation). Also, when two images are displayed in superposition, the color of one image may obscure the characters contained in the other image. To solve the problem above, there have been offered a device having a function of preventing a distortion in the video near the boundary portion by adjusting the saturation near the boundary portion when two images are displayed in superposition (See Japanese Patent No. 2713677), and a device having a function of adjusting the color so that the character and the background image may not have the same color (See JP-A-8-211860).
However, in the conventional STB, since the OSD image is the menu screen for setting various parameters, the user could not adjust the color of the OSD image. Accordingly, the OSD is displayed with the preset color alone, resulting in a problem that the user could not display the OSD image with the color according to the user's own preference or change the color of the OSD image according to the video of the program on which the OSD image is superposed.